Polyvinyl alcohol (PVOH) is a useful polymer as it exhibits excellent tensile and impact strengths, abrasion resistance, and interfacial properties, among other advantageous properties. As such, PVOH is used in films, fibers, paper processing, adhesives and numerous other end products.
PVOH films may be used, for example, in unit dose packaging films, as an oxygen barrier film, and in polarizing films. PVOH/iodine complex films, for example, are an excellent polarizing material used in liquid crystal displays. PVOH may form a complex with iodine as the polyiodide ions interrupt the intermolecular hydrogen bonds. Unfortunately, iodine may desorb from the complex under hot and humid conditions. Desorption of iodine is especially troublesome when the PVOH is atactic, e.g., having a diad syndiotacticity of less than about 53%. Syndiotactic PVOH exhibit a lower degree of desorption, as described in “Preparation of Syndiotacticity-Rich High Molecular Weight Poly(vinyl alcohol)/Iodine Polarizing Film with High Water Resistance,” by Man Ho Han and Won Seok Lyoo, J. Applied Polymer Science, Vol. 115, 917-922 (2010).
Unfortunately, syndiotactic PVOH exhibit a strong intramolecular hydrogen bond, as described in “Properties of highly syndiotactic poly(vinyl alcohol),” by Yoshitaka Nagara et al., Polymer, Vol. 42, 9679-9686 (2001). The strong intramolecular hydrogen bond results in a decrease in solubility of syndiotactic PVOH in solvents, including water, DMSO, ethylene glycol, and glycerol, among others. For example, as reported therein, water temperatures of 127° C. may be required to dissolve 0.1 g syndiotactic PVOH in a deciliter of water.
Decreased solubility in solvents may results in use of harsher operating conditions, more toxic solvents, and difficulties in process operations when forming the polymer, such as due to the formed polymer falling out of solution and agglomerating on agitators, reactor walls, and other unit operations.
Decreased solubility in solvents may also result in the need for harsher operating conditions, more toxic solvents, and difficulties in converting the syndiotactic polymer to useful end products, such as films.